Method for determining the resolution of blood glucose

This application is a continuation of U.S. patent application Ser. No. 10/771,333, filed Feb. 5, 2004, now U.S. Pat. No. 7,089,122 and entitled METHOD FOR DETERMINING THE RESOLUTION OF BLOOD GLUCOSE.

1. Field of the Invention

The present invention generally relates to a method for determining the concentration of blood glucose, and more particularly to a method for determining a peak value of a rising curve to determine the concentration of blood glucose.

2. Description of the Prior Art

In the past, many systems have been developed for monitoring blood characteristics. For example, devices have been developed which are capable of determining such blood characteristics as blood oxygenation, and blood glucose concentration. However, significant difficulties exist when attempting to specifically determine blood glucose concentration accurately using noninvasive blood monitoring systems such as by means of spectroscopic measurement.

The difficulty in determining blood glucose concentration accurately may be attributed to several causes. Firstly, within the bloodstream, the blood glucose is typically found in very low concentrations (e.g., on the order of 100 to 1000 times lower than hemoglobin) so that such low concentrations are difficult to detect noninvasively, and require a very high signal-to-noise ratio. Additionally, with spectroscopic methods, the optical characteristics of glucose are very similar to those of water that is found in a very high concentration within the blood. Thus, where optical monitoring systems are used, the optical characteristics of water tend to obscure the characteristics of optical signals due to glucose within the bloodstream.

Furthermore, dry phase reagent test strips incorporating enzyme-based compositions are used extensively in clinical laboratories, physicians' offices, hospitals, and homes to measure the concentration of the compositions in the biological fluids. These strips have, for example, measured glucose, cholesterol, proteins, ketones, phenylalanine, or enzymes in blood, urine, or saliva. Measuring glucose concentration in samples of whole blood is a particularly common use. In fact, test strips have become an everyday necessity for many of the nation's several million people with diabetes.

Some test strips contain a testing reagent that turns a different shade of color depending on the concentration of glucose in a blood sample that has been applied to the strips. The blood glucose concentration is measured by inserting a strip into a meter that is basically a reflectance photometer, which determines the concentration from the change in color caused by the reaction between the testing reagent and blood glucose. The testing reagent typically contains an enzyme, such as glucose oxidase, which is capable of oxidizing glucose to glucose acid lactone and hydrogen peroxide; an oxidizable dye; and a substance having peroxidative activity, which is capable of selectively catalyzing oxidation of the oxidizable dye in the presence of hydrogen peroxide.

An object of the present invention is to provide a method for calculating the concentration of blood glucose by the relationship between a rising curve and the blood glucose concentration. The concentration of the blood glucose could be obtained from calculating these known values which include the slope on the peak point, resistance, reference resistance, reference voltage, and the average peak value obtained from calculating the plurality of peak values after a pre-set sampling time.

It is another object of the present invention to obtain the maximum of the peak values by using the property of the first differential of the peak value being greater than zero.

Another object of the present invention is to obtain the different heights of the peak values after different pre-set sampling times and using them to make a mapping table.

It is a further object of the present invention to determine the blood glucose concentration according to the different voltages en in the mapping table.

According to the above-mentioned objects, the present invention provides a method of determining the concentration of the blood glucose corresponding with the peak value of the rising curve. The peak value of the rising curve is the basis for determining the blood glucose concentration in the present invention. The concentration of the blood glucose could be obtained from calculating the given values, which include the slope on the peak point, resistance of the determining circuit, reference resistance, reference voltage, and the average peak value obtained from calculating the plurality of peak values after the pre-set sampling time. Furthermore, the mapping table can be created by recording the variable peak values corresponding to the variable pre-set sampling times, and referencing the mapping table to obtain the different concentration of blood glucose for different output voltages.

The foregoing aspects and many of the advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings.

FIG. 1 is a schematic diagram showing how the peak value is used to determine the concentration of the blood glucose in accordance with a method disclosed herein;

FIG. 2 is a schematic diagram showing the relationship between the rising curve and the operation amplifier in accordance with a method disclosed herein;

FIG. 3 is a flow chart showing the steps for determining the concentration of the blood glucose by using the peak value in accordance with a method disclosed herein;

FIG. 4 is a schematic diagram showing the rising curve of the blood glucose concentration in accordance with a method disclosed herein; and

FIG. 5 is a schematic diagram showing the rising curves for the different blood glucose concentration solutions in accordance with a method disclosed herein.

An appropriate and preferred embodiment will now be described in this section. It should be noted, however, that this embodiment is merely an example and can be variously modified without departing from the scope of the present invention. The present invention provides a performance method described as follows:

First, the blood glucose solution is placed on the test strip with the test reagent or catalyst such as an enzyme, wherein the test reagent will react with the blood glucose solution to generate the oxidation reduction reaction to generate an analog source. Then, the analog source is input into a determining circuit of a determining meter that converts an analog signal from the analog source into a digital signal, and then outputs the digital signal to a display apparatus.

Referring to FIG. 1 , a schematic diagram shows the steps for determining the blood glucose concentration by utilizing the peak value. Reference number 10 denotes the analog source, which is generated from the chemical reaction between the blood glucose solution and the test reagent with the enzyme that acts as a catalyst. A treatment device 12 receives the analog signal from the analog source, converts the analog signal into a digital signal, and outputs the results from the digital signal into a display apparatus 14 . The treatment device comprises an OA (Operational Amplifier) 12 A with at least one resistor. When the blood glucose concentration increases, the OA resistance is also increases. The analog signal from the OA is converted by an AFE (Analog Front End) 12 B into the digital signal. The AFE 12 B can be an ADC (Analog to Digital Converter). Next, the digital signal from the AFE 12 B is processed by a MCU (Microprocessor Control Unit) 12 C. The processed digital signal is output from the MCU 12 C to the display apparatus 14 . The display apparatus 14 then displays is a curve diagram.

FIG. 2 is a schematic diagram illustrating the relationship between the rising curve of the blood glucose concentration and the operational amplifier. The blood glucose solution reacts with the test reagent to produce the analog signal. The height of the analog curve is determined by the blood glucose concentration and the resistance, the resistance increasing with the increase of the blood glucose concentration. After the analog signal is transferred into the operation amplifier, the analog signal will be transformed into the output voltage (V out ) according to known values: the slope on the peak point, the resistance (R G ) in the operational amplifier, the reference resistance (R f ), and the reference voltage (V ref ).

FIG. 3 is a schematic diagram illustrating the flow steps for determining the blood glucose concentration from the peak value. In step 20 the blood glucose solution reacts with the catalyst to produce the analog signal. The chemical reaction may be an oxidation reduction reaction. Step 22 treats the analog signal source and produces a wave diagram. At step 24 , the maximum value of the wave diagram is obtained after the pre-set sampling time. In the first preferred embodiment of the present invention, the average peak value could be calculated at step 26 A from the plurality of peak values after the pre-set sampling time. At step 26 B, the method determines the blood glucose concentration by calculating the average peak value. In the other preferred embodiment at step 28 A, a mapping table is created from the plurality of peak values.

The mapping table shows the relationship between the blood glucose concentration and the output voltage. At step 28 B, the blood glucose concentration is calculated by obtaining the output voltage value of an unknown blood glucose solution and comparing it with the mapping table.

FIG. 4 is a schematic diagram illustrating the rising curve of the blood glucose concentration. The peak value is obtained after the pre-set sampling time when the first differential is larger than zero, y(t 1 )−y(t 0 )>0, which is the difference between the first time (t 1 ) and the initial time (t 0 ) with a result that is larger than zero. In the first preferred embodiment of the present invention, the average peak value could be obtained by adding and averaging the plurality of peak values after the pre-set sampling time. After calculating the average peak value, the slope of the peak point, resistance, reference resistance, and reference voltage, are used for obtaining the blood glucose concentration.

FIG. 5 is a schematic diagram illustrating the rising curves of the different concentrations of the blood glucose solutions. In FIG. 5 , curves C 1 , C 2 and C 3 represent the different blood glucose concentrations. Likewise, if the first differential is larger than zero, the method of the present invention identifies the peak value of the curve and creates a mapping table of the output voltage and blood glucose concentration from the plurality of peak values. Therefore, the actual blood glucose concentration is obtained from the output voltage value of an unknown blood glucose solution by finding the corresponding value in the mapping table.

While this invention has been described with reference to illustrative embodiments, the description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the invention, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.